1. Field of the Invention
The invention generally relates to a frame and a method of forming a corner of the frame. More specifically, the invention relates to joining the frame at a corner without the use of fasting devices.
2. Description of the Related Art
Traditional frames, such as those for windows or doors which support a screen cloth or a pane of glass, are formed from four sides that are connected to form four corner joints. The sides surround an open space of the frame and, in traditional frames, the sides are secured together at the corner joints using welds or other fasteners, such as a corner lock or a corner key.
Some frames have been constructed from a single continuous frame section having one corner joint instead of using separate sides that are each connected to form four separate corner joints. One such frame is disclosed in U.S. Pat. No. 5,881,525 to Riegelman et al. (the '525 patent). The '525 patent discloses a continuous frame section formed from a flat strip of metal that is folded over onto itself to define a hollow tube and a flange extending from the tube. A square end and a mitred end are formed at opposite ends of the continuous frame section. A mitre cut, a square cut, a locking tab, and a locking strip are formed at three locations along the continuous frame section. Additionally, two locking holes are defined by the hollow tube near opposite ends of the continuous frame section. The continuous frame section is folded at each of the mitre cuts to bring the square cuts within the mitred cuts and define three fold corners. The locking tab engages, and is retained within, the locking strip for each fold corner. An L-shaped bracket, i.e., a corner lock or corner key, is used to bring the opposing ends of the continuous frame section together to form the fourth corner joint, i.e., a locking corner. The bracket includes arms and hooks that extend from the fourth corner joint at a 90 degree angle. An arm and a corresponding hook are inserted into the mitred end. Next, the other arm and corresponding hook are inserted into the beveled end where the beveled end is brought over the square end. After insertion of the arms and corresponding hooks, a hook engages each of the locking holes to bring the opposing ends together and lock the fourth corner. Accordingly, this type of fourth corner requires an additional piece, i.e., the L-shaped bracket, to complete the frame. Without the L-shaped bracket, the frame cannot be locked at the fourth corner. This added piece adds additional cost to assembling the frame due to the additional time and material associated with the L-shaped bracket.
Other frames have been constructed from a single continuous frame section, folded upon itself, to form the corner joint. One such frame is disclosed in U.S. Pat. No. 2,952,342 to Schnittker (the '342 patent). The '342 patent discloses a continuous frame section formed from a flat strip of metal that is folded over onto itself to define a hollow tube and a flange extending from and along the tube. Mitre cuts are formed at three spaced locations along the continuous frame section. An insertion tab extends from a first end of the continuous frame section and a locking tab extends from a second end of the continuous frame section. Additionally a locking slot is defined in the continuous frame section, adjacent the locking tab. The continuous frame section is folded about each of the mitre cuts to form three fold corners and the ends are brought together to form the corner joint. When the ends are brought together, the insertion tab is inserted into the locking slot, and the locking tab and the insertion tab are bent away from each other to “lock” the frame together at the fourth corner. The additional steps of bending each of the tabs is cumbersome and, therefore, adds additional time to assemble the frame which translates into additional cost to manufacture the frame.
Accordingly, it would be advantageous to produce a frame where the corner joint is formed by only bringing the ends together where fasteners, such as locking keys, and/or additional steps, such a bending locking tabs are eliminated. Elimination of these parts or steps would save time and cost to manufacture the frames.